Flu shots or nasal sprays are used to inoculate people of all ages, especially the young or old, to prevent strains of influenza common during the winter or spring. Starting in October, all Ontario residents 6 months or older can get a free flu vaccine from a family doctor, pediatrician, or public health unit. People with a valid health card, ages 5 years and older, can also get their free flu shot from a participating pharmacy.